/**
 * Copyright (c) 2009, Christian Schneider
 * All rights reserved.
 * 
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 * 
 * - Redistributions of source code must retain the above copyright notice, this
 *    list of conditions and the following disclaimer.
 *  - Redistributions in binary form must reproduce the above copyright notice,
 *    this list of conditions and the following disclaimer in the documentation
 *    and/or other materials provided with the distribution.
 *  - Neither the names of the authors nor the names of its contributors may
 *    be used to endorse or promote products derived from this software without
 *    specific prior written permission.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */
package name.cs.csutils;

import java.util.Enumeration;
import java.util.NoSuchElementException;

public class FilteringEnumeration<E> implements Enumeration<E> {

    private Enumeration<? extends E> srcEnumeration;
    private E next;
    private Filter<E> filter;

    public FilteringEnumeration(
            Filter<E> filter,
            Enumeration<? extends E> srcEnumeration) {
        if (filter == null || srcEnumeration == null) {
            throw new IllegalArgumentException("filter="+filter+",enumeration="+srcEnumeration);
        }
        this.filter = filter;
        this.srcEnumeration = srcEnumeration;
        align();
    }
    
    private void align() {
        next = null;
        while (next == null && srcEnumeration.hasMoreElements()) {
            E item = srcEnumeration.nextElement();
            if (filter.test(item)) {
                next = item;
            }
        }
    }
    
    public boolean hasMoreElements() {
        return next != null;
    }

    public E nextElement() {
        if (!hasMoreElements()) {
            throw new NoSuchElementException();
        }
        E result = next;
        align();
        return result;
    }

}
